1,1,2-Trichloro-1,2,2-trifluoroethane (CFC-113) was used for many years as a calibration fluid, as well as for cleaning applications, but its use was discontinued due to concerns linking chlorofluorocarbons (CFCs) with the depletion of ozone in the earth's atmosphere. 2,3-dihydrodecafluoropentane (C5H2F10), which is also known as hydrofluorocarbon-4310mee (“HFC-4310mee”), was developed more than a decade ago as a replacement for ozone-depleting solvents such as 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113).
HFC-4310mee, which is marketed by the DuPont Company (Wilmington, Del.) under the trade name of Vertrel® XF, is typically used as an industrial cleaning and rinsing agent, drying fluid, particulate remover, solvent and dispersion medium, heat transfer fluid, or dielectric fluid. Vertrel® XF fluid was substituted for CFC-113 in many cleaning applications, but was not a good candidate as a calibration fluid because it is a mixture of the two diastereomers (HFC-4310-mee-erythro and HFC-4310-mee-threo), and does not have a constant boiling temperature at a given pressure. Also, the density of the fluid is not reproducible because the composition of the Vertrel® XF fluid is not constant. HFC-4310mee is generally not a chemically pure compound since it consists of the threo and erythro diastereomers of 2,3-dihydrodecafluoropentane (C5H2F10), in addition to other impurities in some commercial formulations.
It would be advantageous to separate the threo and erythro isomers to produce a pure product containing only a single isomer. By separating the diastereomers of HFC-4310mee to produce a purified HFC-4310mee-threo or a purified HFC-4310mee-erythro product, these pure diastereomers can be used as calibration fluids for analytical instrumentation with constant boiling temperatures and known liquid density.
As a new type of solvent with immeasurable vapor pressure, room-temperature ionic liquids are being studied for diverse applications, such as chemical separations, as unique reaction media, and as environmentally friendly (“green”) solvents. Several processes utilizing ionic liquids have been commercialized, such as the BASIL™ acid scavenging technology from BASF (Ludwigshafen, Germany). Although U.S. patent application Ser. No. 11/525,466 (WO 07/38363) discloses a method for using an ionic liquid to separate different compounds that are close-boiling or azeotropic components in a mixture of the compounds, a need still remains for improved processes to separate diastereomers from within a single compound.